An electrochemical technique is simple and costs little, and thus has been widely used as a biosensor using a product of a catalytic reaction such as a product of an enzymatic reaction. Recently, an array-type sensor provided with a plurality of microelectrodes has been developed with miniaturization of electrodes in a detecting unit (see Japanese Patent Application Laid-Open No. 2002-071620).
An array-type sensor is capable of acquiring two-dimensional positional information with respect to the same specimen and dynamic changes in substance distribution. Further, an array-type sensor may perform multichannel detection through reactions of electrodes set in array with specific, different specimens (See Kenichi Kojima, Atsunori Hiratsuka, Hiroaki Suzuki, Kazuyoshi Yano, Kazunori Ikebukuro, and Isao Karube, “Analytical Chemistry” 2003, 75, p. 1116-1122).
Meanwhile, a measuring device for sampling and measuring in a microchannel is used as a microfluidic device. Niwa et al. have proposed an online biosensor including a microchannel and a thin layer channel in combination and have conducted a continuous quantitative analysis of a trace amount of a sample (Japanese Patent Application Laid-Open No. H11-083784).
However, those techniques alone hardly allow separation and detection of a plurality of detection target substances in an actual measurement sample (such as blood) in the same channel at the same time. For example, the measurement sample may be distributed to a plurality of channels to detect the detection target substances in the respective channels, but a required amount of the measurement sample increases. In the case where a trapping site for trapping a plurality of detection target substances in the specimen is provided in a channel, a reaction product of a catalytic reaction, which is derived from the detection target substances with a catalyst, is often the same substance for some of the detection target substances. The product of a catalytic reaction diffuses in a liquid, and thus, from which detection target substance the product was produced was hardly identified with one detecting unit (such as an electrode).